Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $104.74   9.194%   $114.3698   $114.37   $114.35   $114.40  
  Purchase #2 $216.93   8.785%   $235.9873   $235.99   $236.00   $236.00  
  Purchase #3 $34.42   6.159%   $36.5399   $36.54   $36.55   $36.50  
  Purchase #4 $186.56   11.656%   $208.3054   $208.31   $208.30   $208.30  
  Purchase #5 $60.69   8.843%   $66.0568   $66.06   $66.05   $66.10  
  Purchase #6 $81.59   12.351%   $91.6672   $91.67   $91.65   $91.70  
  Purchase #7 $239.28   8.486%   $259.5853   $259.59   $259.60   $259.60  
  7 purchase totals = $924.21       $1,012.5117   $1,012.53   $1,012.50   $1,012.60